For service and parts needs, visit your dealer. You will receive genuine GM parts and GM-trained and supported service people.
Genuine GM parts have one of these marks:

Vehicle Care
California Proposition 65 WarningInstallation Procedure
Cut the rear side rail in corresponding locations to fit the remaining
original panel. The sectioning joint should be trimmed to allow a
gap of one-and-one-half-times the metal thickness at the sectioning joint.
Create a 50 mm (2 in) backing plate from the unused portion of the
serv ...
Collision Repair
Specifications
Point-to-point measurements are for reference only. All measurements are
given in millimeters. Use these measurements for diagnosing
and estimating. Point-to-point measurements are duplicated with tram bar
pointers set at equal lengths. All die marks, holes, slots, and
fast ...
Safety System Check
Now and then, check that the safety belt reminder light, safety belts, buckles,
latch plates, retractors, and anchorages are all working properly.
Look for any other loose or damaged safety belt system parts that might keep
a safety belt system from doing its job. See your dealer to have it rep ...